Electrolytic process



Patented June 30, 1925.

UNITED STATES CHARLES J. THATCHER, OF NEW YORK, N. Y.

ELECTROLYTIC rnocns's.

No Drawing.

To all whom it may concern:

Be it known that I, CHARLES J. THATCHER, a citizen of the United States,and a resident of New York, in the county of vNew York and State of NewYork, have invented certain new and useful Improvements in ElectrolyticProcesses, of which the following is a speeificatiom The inventionrelates to electrolytic processes; and its object isto prepare aplurality of products, particularly organic products, by oneelectrolysis.

By way of example, the novel process will be described as applied to theproduction of anthraquinone from anthracene and of benzidine fromazoxybenzol or azobenzol. It is to be understood, however, that theprocess may be applied to the oxidation and reduction, by oneelectrolysis, of other compounds, either organic or inorganic, and whichare either solid or liquid, and either insoluble or soluble in theelectrolyte used.

provided the products resulting from the electrolysis can besubstantially completely separated from the respective anolyte andcatholyte after each operation or series of operations.

Apparatus suitable for thispurpose may consist of a single cell adaptedto maintain effective separation of the anolyte and catholyte liquors,as by a diaphragm of the charactor, for example, set forth in my U. S.Iratters Patent No. 1,291,253. Or, as descrlbed U S. Letters Patent No.

' and shown'in my one, and

1,397,562, the apparatus may consist of a plurality of electrolyticcells connected preferably in series or series parallel, and havingseparated anode andcathode compartments. The cells should preferably beof a type providing for vigorous agitation of the electrolyte, and inwhichthe agitation tends to maintain a homogenous mixture of suspendedor dissolved substances to be o'xidized and reduced, and which mightotherwise settle out at the bottom, r, other wa s. A suitable cell forthis purpose is that s own and described in my U. S. Letters Patent No.1,388,216.

The process itself will be described as adapted to the electrolyticoxidation of an acceptor, such as anthracene'to anthraquin- Y reductionof a difi'erent acceptor such as azoxybenzol to benzidine by oneelectrolysis. uch oxidation and reduction, producing two differentproducts, I find can or float at the or causes concentration varlations1n Application filed April 2, 1923! Serial No. 629,419.

be attained by the use of an electrolyte con-..

taining chromium ions both as anodic and cathodic catalysers,depolarizers or carriers of oxygen and hydrogen to the said acceptors.Other suitable depolariz ers or catalysers, such as vanadium, manganese,cerium or titanium ions, or combinations thereof; or other suitable ionspossessing several different valencies or degrees of oxidation, may beutilized, and in concentrations suitable for or customary inelectrolytes.

In the oxidation of anthracene and the reduction of azoxybenzol with anelectrolyte containing chromium ions, electricity for the electrolysisis to be supplied in any well known manner to a suitable cell or cells(not shown); and the initial electrolyte, both as to the anode andcathode portions, may consist of an aqueous solution of sodiumbichromate and sulphuric acid in the proportions of one pound of theformer and two pounds of the latter to each gallon of solution, althoughother suitable portions may, of course, be used. At the initial stage ofthe process, the electrolysis is to be continued until substantially allof the sodium bichromate of the cathode portion of the electrolyte hasbeen reduced to chromium sulphate. Or, as an alternative, the cell maybe initially-supplied with an electrolyte containing chromium sulphateand sulphuric acid. such as spent chromium liquors resulting fromoxidation of anthracene to anthraquinone. In suchease, the spent liquorswill or may contain chromium sulphate, sodium sulphate and sulphuricacid in proportions substantially the same as those resulting from theelectrolytic reductions of the sodium bichromate. and sulphuric acidsolution hereinbefore specified. Electrolysis prior to the introductionof acceptors, for

oxidation and reduction, will then not be necessary.

With a catholyte which is substantially free from sodium bichromate andan anolyte consisting either of the specified solutions of sodiumbichromate and sulphuric acid, or, chromium sulphate, sodium sulphateand sulphuric acid, there is added to the catholyte, azoxybenzol, as forexample, in the proportion ofone-half to one pound thereof per gallon ofeatholyte. To the anolyte,

there is added anthracene in the proportion,

for exam le, of one-half to one pound there of to eaci gallon ofanolyte. Electrolysis" is then started, resumed or continued, ac-

companied preferably by a vigorous agitation of the anolyte and catholte 1n such a way that the acceptors are we I distributed throughout thebody of the electrolyte. Su1t-' able current density will be three tofive reduced and substantially all of the anthracene is oxidized. Insuch an electrolysis, chromium ions act as a depolarizer or carrier ofthe hydrogen liberated at the cathode to the azoxybenzol, reducing iteventually to hydrazobenzol, which latter compound is converted intobenzidine by the sulphuric acid present in the electrolyte. The end re-'sult is that all or substantially all of the azoxybenzol is convertedinto benzidine sulphate. which is insoluble in and may be separated fromthe catholyte, as by filtration. At the same time, the bichromate ionsformed at the anode, under the conditions of the electrolysis, oxidizethe anthracene suspended in the anolyte to anthraquinone, which is alsoinsoluble in and may readily be separated from the anolyte, as byfiltration.

The end result, of the electrolysis, therefore, is a catholytecontaining chromium sulphate, sodium sulphate and sulphuric acid, and ananolyte which will be of substantially the same composition, ifsufiicient anthracene has been used to reduce all the sodium bichromateoriginally present or formed by the electrolysis. It is desirable thatthis be done in order to have for the next operation or for thecontinuation of the same operation, an electrolyte which issubstantially free from. sodium bichromate. If all t 1e sodiumbichromate has not been used up in the oxidation of the anthracene, anac ditional amount of anthracene may be oxidized with the resultinganolyte, by filtering ofi' 'the anthraquinone formed and using enoughanthracene to reduce substantially all of the remaining sodiumbichromate to chromium sulphate.

It will also be understood tion of the anthracene to anthraquinone bythe bichro'mate electrolyte formed at the anode may be entirelyeffected. if desired,

subsequent to the electrolysis and outside the electrolytic apparatus,as by collecting an amount of the electrolyte containing suflicientbichromate to'oxidize chemically any desired amount of anthracene. Thisoperation may be accomplished by well known methods and under well knownconditions that the oxidain a suitable rat or other container (notshown) and extraneous to the electrolytic apparatus.

In either case, the anolyte, remaining from tration of the catholytewill have corrc-,.

spondingly diminished. For this reason, the liquors or the electrolysisshould be reversed after each operation, that is to say the anolyteliquors should be used' as a catholyte liquor and the catholyte liquorasthe anolyte liquor in the continuation of the operation or thesucceeding electrolysis, whereby the concentrations in sulphuric acidwill tend to be restored by the said 'migration ofSO ions.

The concentration of sulphuric acid in the catholyte will, moreover, bereduced during electrolysis, by the combination of sulphuric acid withthe benzidine to form benzidine sulphate, as aforesaid. During theelectrolysis, therefore, or after the separation of the benzidinesulphate fromthe catholyte,- a sufficient amount of sulphuric acid istobe added to the catholyte portion of the elec'- trolyte to replenish theamount of sulphuric acid removed in. combination as benzidine sulphate.After this has been done, the remaining catholyte is then to be used asthe anolyte for. a continuation or the next operatlon of the process, asaforesaid.

Operating in cycles in this manner, the electrolyte will maintainsubstantially its initial concentration in chromium and sulphuric acidions during any series of operations; and repeated reductions ofazobenzol and repeated oxidations of 'anthracene can be effected each byone electrolysis, using the same electrolyte over and over againifdesired. a It will be understood that azobenzol or other azo or azoxyderivatives or homologues may be so reduced, and that other compoundsthan anthracene may be so oxidized. It is not necessary, moreover, thatthe final product should be solid and substantially iusolublein the.resulting electrolyte, although that is desirable; for oxidation andreduction products, which can be separated by solvents immiscible in theelectrolyte, or by other suitable means, may be produced by the novelprocess.

It will be understood that in using the word catalyser I intend toimplyany ion or ions-which will either act catalytically or as a depolarizerand carrier of oxygen and which will be respectively oxidized or reducedwith the formation of separable prodacts by the anodic and cathodiccatalyser.

I am aware that separate oxidation and reduction, at different times, ofcertain compounds has been heretofore effected bymeans of electrolytescontaining the same ion; but such oxidations and reductions have beencarried out separately, with re sultant loss of oxygen or hydrogen ineach reduction or oxidation. For a number of years it has been the aimof chemists to effect such an oxidation and a reduction by oneelectrolysis; but this result has first been achieved, so far as I amaware, only by the herein described invention.

I claim 1. The process of electrolytic oxidation of one product andelectrolytic reduction of another product, which consists inelectrolysing an electrolyte separated into an anolyte and catholyte andcontaining ions capable of acting as anodic and cathodic catalysers,introducing into the anolyte and catholyte liquors acceptors capable ofbeing respectively oxidized and reduced thereby and of forming productsseparable therefrom. and separating the resulting products.

2. The process of electrolytic oxidation of one organic product andelectrolytic reduction of another organic product, which consists inelectrolysing an electrolyte separated into an anolyte and catholyte andcontaining ions capable of acting both as anodic and cathodiccatalysers, introducing into the anolyte and catholyte liquors acceptorscapable of being respectively oxidized and reduced therebyfand of.forming products separable therefrom, and separating the re-' s1 I l ti ng products.

:3. The process of electrolytic oxidation of one product andelectrolytic reduction of another product. which consists inelectrolysing an electrolyte separated into an anolyte and catholyte andcontaining ions capable of acting both as anodic and cathodiccatalysers, subsequnetly adding to the anol \'te and catholyte liquorsand While continuing the electrolysis acceptors capable of beingrespectively oxidized and reduced thereby and of forming productsseparable therefrom, and separating the resulting products.

4. The process of electrolytic oxidation of one product and electrolyticreduction of another product, which consists in e1ectrolysiug an aqueoussolution of a chromium compound and sulphuric acid separated into ananolyte and catholyte, introducing into the anolyte and catholyteliquors acceptors capable of bemg respectively oxidized and reducedthereby and of forming products separable therefrom, and separating theresulting products.

5. The process of electrolytic oxidation of an oxidizable product andelectrolytic reduction of a reducible product, which consists inelectrolysing an aqueous solution of sodium bichromate and sulphuricacid sepaiaited into an anolyte and catholyte, introducing, after thesubstantial reduction ofthesodium bich'romate of the catholyte portion,into the anolyte and catholyte liquors acceptors capable of beingrespectively oxidized and reduced thereby and of forming productsseparable therefrom, and separating the resulting products.

(i. The process of electrolytic oxidation of an oxidizable product andelectrolytic reduction of a reducible product, which consists inelectrolysing an aqueous solution of' sodium bichromate and sulphuricacid in the proportion of one (1) pound of the former and two (2) poundsof the latter per gallon of solution, separated into an anolyte andcatholyte, introducing, after the substantial reduction of the sodiumbichromate ot' the catholyte portion, into the an olyte and catholyteliquors acceptors capable of being respectively oxidized and reducedthereby and of forming products separable therefrom, and separating theresulting products.

7. The process of electrolytic oxidation of an oxidizable product andelectrolytic reduction of a reducible product, which consists inelectrolysing an aqueous solution of sodium bichromate and sulphuricacid in the proportion of one (1) pound ofthe former and two (2) poundsof the latter per gallon of solution, separated into an anolyte andcatholyte, and at a temperature of from to 90 C., introducing, after thesubstantial reduction of sodium bichromate of the catholyte portion,into the anolyte v and catholyte liquors acceptors capable of beingrespectively oxidized and. reduced thereby and of forming productsseparable therefrom, and separating the resulting products.

8. The process of electrolytic oxidation of one product and electrolyticreduction of another product, which consists in electrolysing anelectrolyte separated into an anolyte and catholyte and containing ionscapable of acting both as anodic and cathodic catalysers, introducinginto the anolyte and catholyte liquors acceptors capable of beingrespectively oxidized and reduced thereby and of forming productsseparable therefrom, separating the resulting products, re plenishingions depleted in the electrolysis, and repeating the operation.

9. The process of oxidation of anthracene to anthraquinone and reductionof benzol compounds to benzidine, which consists in electrolysing anelectrolyte separated into an anolyte and catholyte and containing ionscapable of acting both as anodic and cathodic catalysers, introducinganthracene into the anolyte and the benzol compound into the catholyte,and separating the resulting products therefrom.

10. The process of electrolytic oxidation of anthracene to anthraquinoneand the electrolytic reduction of azoxybenzol to benzidine, whichconsists in electrolysing an aqueous solution of sodium bichromate andsulphuric acid, introducing anthracene into the anolyte and azoxybenzolinto the catholyte, and separating theanthraquinone and benzidinesulphate from the respective liquors.

11. The process of electrolytic oxidation of anthracene to anthraquinoneand electrolytic reduction of azoxybenzol to benzidine,

'WlllCll consists 1n electrolysmg an aqueous solution of sodiumbichromate and sulphuric acid, introducing anthracenc into the anolyteand azoxybenzol into the catholyte, separating the anthraquinone andbenzidine sulphate from the respective liquors, and replenishing thesupply of sulphuric acid of the anolyte.

12. The process of electrolytic oxidation of one product andelectrolytic reduction of another product, which consists inelectrolysing an electrolyte separated into an anolyte and catholyte andcontaining ions capable of acting both as anodic and cathodiccataly'sers, introducing into the anolyte and catholyte liquorsacceptors capable of being respectively oxidized and reduced thereby andof forming roducts separable therefrom, separating t e resultingproducts, and

repeating the operation with anolyte as catholyte and catholyte asanolyte.

13. Electrolytic oxidation and reduction process, with separated anolyteand catholyte and common 'catalyser ions, which in cludes the step ofintroducing therein acceptors capable of bein .respectively oxidized andreduced there y and of forming products separable therefrom.

14. A process of electrolysis for the production of two products, whichconsists in preparing an electrolyte containing ions capable of actin asanodic and cathodic catal'ysers, electro ysing so as to produce ananolyte and catholyte, adding thereto acceptors capable of beingrespectively oxidized and reduced thereby and of forming productsseparable therefrom, and separating the resulting products.

15. A process of electrolysis for the production of two organicproducts, which consist-s in preparing an electrolyte containing ionscapable of acting both as anodic and cathodic catalysers, electrolysingso as to produce-an anolyte and catholyte, adding thereto acceptorscapable of being respectively oxidized and reduced thereby and of forminproducts separable therefrom, and separating the resulting products.

16. A. process of electrolysis for the production of two products, whichconsists in preparing an electrolyte containing ions capable of actingboth as anodic and cathodic catalysers, electrolysing so as to producean anolyte and catholyte, adding thereto acceptors capable of beingrespectively oxidized and reduced thereby and of forming productsseparable therefrom, separating the resulting products, and using theanolyte as catholyte and the catholyte as anolyte in a subsequentoperation.

17. The process of electrolytic oxidation" of anthracenc toanthraquinone and the electrolytic reduction of azoxybenzol tobenzidine, which consists in electrolysing an aqueous solution of sodiumbichromate and sulphuric acid, introducing anthracene into the anolyteand azoxybenzol into the catholyte, separating the anthraquinone andbenzidine sulphate from the respective liquors, and using the anolyte ascatholyte and the catholyte as anolyte in a subsequent operation.

Signed at New York in the county of New York and State of New York this31st day of March, A. D. 1923.

CHARLES J. THATCI-I ER.

